The modern monohull watercraft can be traced back to the hollowed log canoes used by primitive cultures around the world. The long narrow hull of these ancient boats is a very efficient shape in the water, which is an important feature for a vehicle propelled only by human or wind power. In today's world of limited resources and energy an efficient hull shape continues to be a very desirable feature. For a given displacement, a hull with high aspect ratio (the length divided by the width) is much easier to push through the water than a hull with low aspect ratio.
One big disadvantage of a narrow monohull is lateral stability. The narrow hull presents a greater risk of capsize, especially for sailboats. Making the boat wider increases the stability, but creates much more drag though the water. An alternate solution is to keep the narrow hull form, but add ballast in the form of a weighted keel. The heavy ballast adds stability, but the boat is pulled deeper into the water which increases the water displacement and again increases drag.
Early Polynesians developed a clever solution to the problem of maintaining stability in a narrow monohull. The Outrigger canoe adds a secondary hull connected to the first hull by a pair of support arms. This results in a very stable boat that still retains the more efficient narrow hull form. Modern multihull watercraft (catamarans and trimarans) incorporate this idea to achieve significantly improved performance on the water.
As the multihull form developed into the 21st century, it continued to offer many advantages over traditional monohulls, but the design still has several inherent problems. There is a conflict between accommodation space and hull form. The narrow shape of catamaran and trimaran hulls, while highly efficient when moving through the water, also create awkward interior spaces. Humans prefer accommodations with roughly square-shaped floor plans, not uncomfortable tunnel shapes that are neither convenient nor inviting for any activity except sleep. Widening the hull improves the accommodation space but seriously degrades the performance of the boat.
Conventional multihulls have a further problem of awkward boarding and disembarking. This is particularly true for large catamarans on a side dock, where the high freeboard (the distance between the deck and the water) requires a ladder or portable staircase for boarding. The high freeboard also results in high amounts of lateral windage. Compensating for this windage while under way wastes a significant amount of energy, and docking and maneuvering in a tight marina can be difficult as the wind pushes the boat off course.
Conventional multihulls have a further problem of awkward storage and deployment of a shore craft (dinghy). Storage on deck takes up valuable space and may also require a crane for deployment. Dinghy davits (typically a pair of metal arms used for both storage and deployment) are also not an optimum solution in terms of convenience and aesthetic appeal. In either case, boarding and exiting the dinghy can be awkward and dangerous because there is no suitable boarding platform.
The present invention addresses all of these problems while providing additional benefits.